A problem with many known types of oscillator circuit is that variations in temperature cause changes in the oscillation frequency. In some cases the oscillation frequency can increase with temperature, whereas in other cases the oscillation frequency can decrease with temperature For example, consider oscillator circuits which rely on repeated charging and discharging cycles of a capacitor to generate an oscillating voltage signal. A problem with such oscillator circuits can be that the rate of current flow on and off the capacitor C increases with increasing temperature As a result, the capacitor charges and discharges faster at high temperatures and thus reaches respective upper and lower voltage limits in less time. This means that the frequency of the oscillating signal increases with temperature and hence such oscillators are unreliable in timing applications.